Cue ball control is one of the most important aspects of being a top-notch pool player. If you can position the cue ball where you want after a shot, you will be in good shape for your next shot and stand a good chance of running the table and winning the game.
Being aware of, and using the tangent line to your best advantage, is an important part of good position play. The following video will help you understand and better use the tangent line and any english that you wish to use with it.
If you can develop your ability to position the cue ball after the shot to a high degree, you will definitely win more pool games.